Where these formulas come from
B.J. Devine published the first formula in 1974 to standardise gentamicin dosing — it produced a single height-derived weight figure to plug into the mg/kg-of-IBW dose. Robinson (1983), Miller (1983) and Hamwi (1964) refined the relationship for different body types. None of them were intended as wellness targets. Today, ARDSnet ventilator settings, vancomycin loading doses, and intra-operative neuromuscular blockade all dose by IBW (or sometimes “adjusted body weight” for obese patients).
Why we don’t recommend it as a weight goal
Health Canada’s Healthy Eating guidelines, the 2020 Obesity Canada Adult Practice Guidelines, and most Registered Dietitian recommendations explicitly counsel against weight goals based on BMI or IBW alone. The literature shows that a 5–10 % loss of starting weight produces most of the metabolic health benefit; driving toward an arbitrary “ideal” doesn’t add much and often backfires (cyclic dieting, disordered eating, sarcopenic weight regain).
For lifestyle planning, use the healthy-weight range
The BMI 18.5–24.9 healthy-weight range calculator is a better reference for goal-setting in a lifestyle context: it returns a band, not a point estimate, and explicitly treats body composition as out of scope. For metabolic markers that matter more than weight (waist circumference, A1C, blood pressure, lipid panel), see your family doctor.